PubMed2004
OBJECTIVE: To determine the accuracy and repeatability of an automated quantitative fluoroscopic imaging system for measuring knee laxity. DESIGN: Cadaveric validation study. BACKGROUND: Current methods of measuring anterior-posterior laxity lack sufficient accuracy and repeatability. A commercially developed fluoroscopic software package, capable of measuring laxity, required validation. METHODS: Five human cadaveric knees were used. A constant force of 130 N was applied anteriorly and posteriorly in turn to the tibia of each knee with the femur fixed in 30 degrees and 90 degrees of flexion. Quantitative fluoroscopic measurements of anterior-posterior laxity were determined using image analysis software. Fluoroscopic results were compared to the true anterior-posterior displacements of the tibia, which were simultaneously recorded using linear transducers directly attached to the cadaveric specimens. RESULTS: The quantitative fluoroscopic method underestimated laxity by an average of 0.40 mm with a root mean square error of 0.49 mm. The 95% confidence intervals for anterior and posterior laxity error were calculated to be -0.99 to 0.25 mm and -0.89 to 0.03 mm, respectively, where a negative error represents an underestimation. CONCLUSIONS: The quantitative fluoroscopic method offers a dramatic improvement in accuracy over current laxity measurement techniques and acceptable repeatability for assessing ligament damage. RELEVANCE: The considerably more accurate, validated measurement system of this study could improve ligament assessment and diagnosis, and the recognition of injuries otherwise undetected with current methods.